Previously, for example, Patent Document 1 discloses a control apparatus for an engine having a cylinder halting mechanism which is capable of maintaining intake and exhaust valves in a valve closed state. This conventional control apparatus is configured to determine whether an abnormality (stopping failure) has not occurred in a stopping operation of the intake and exhaust valves based on an output value of an exhaust gas sensor when the intake and exhaust valves of some of cylinders are closed and stopped associated with a reduced-cylinder operation.
It is noted that the applicant of the present invention recognizes the below described documents including the above described document as the related art of the present invention.